16440721 has 8 divisors (see below), whose sum is σ = 17987904. Its totient is φ = 14902320.

The previous prime is 16440673. The next prime is 16440727. The reversal of 16440721 is 12704461.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 16440721 - 2⁹ = 16440209 is a prime.

It is a super-3 number, since 3×16440721³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (16440727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2100 + ... + 6106.

It is an arithmetic number, because the mean of its divisors is an integer number (2248488).

Almost surely, 2^16440721 is an apocalyptic number.

16440721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16440721 is a deficient number, since it is larger than the sum of its proper divisors (1547183).

16440721 is a wasteful number, since it uses less digits than its factorization.

16440721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4391.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 16440721 is about 4054.7158963360. The cubic root of 16440721 is about 254.2769263560.

It can be divided in two parts, 16440 and 721, that added together give a square (17161 = 131²).

The spelling of 16440721 in words is "sixteen million, four hundred forty thousand, seven hundred twenty-one".